A simple, mild and efficient method for the synthesis of pyrazolopyridine based spirooxindoles by the three-component reaction has been developed using sulfamic acid (H2NSO3H) as a green catalyst. The method involves use of water as a solvent which makes it eco-friendly. The catalyst used is readily available and is prominent for short reaction time, operational simplicity and high yields. After completion of the reaction the catalyst could be recovered and reused for up to four cycles without loss in catalytic activity. Employing this method a library of 34 compounds has been synthesized and investigated for their cytotoxicity against a panel of three human cancer cell lines. Some of the compounds like 4o and 4p exhibited remarkable cytotoxicities with IC50 values of 0.35μM and 1.92μM against MDA-MB-231 cell line.